.TH std::is_unsigned 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::is_unsigned \- std::is_unsigned

.SH Synopsis
   Defined in header <type_traits>
   template< class T >              \fI(since C++11)\fP
   struct is_unsigned;

   std::is_unsigned is a UnaryTypeTrait.

   If T is an arithmetic type, provides the member constant value equal to true if T\fB(0)\fP
   < T(-1): this results in true for the unsigned integer types and the type bool and
   in false for the signed integer types and the floating-point types.

   For any other type, value is false.

   If the program adds specializations for std::is_unsigned or std::is_unsigned_v, the
   behavior is undefined.

.SH Template parameters

   T - a type to check

   Helper variable template

   template< class T >                                           \fI(since C++17)\fP
   inline constexpr bool is_unsigned_v = is_unsigned<T>::value;



Inherited from std::integral_constant

.SH Member constants

   value    true if T is an unsigned integral type, false otherwise
   \fB[static]\fP \fI(public static member constant)\fP

.SH Member functions

   operator bool converts the object to bool, returns value
                 \fI(public member function)\fP
   operator()    returns value
   \fI(C++14)\fP       \fI(public member function)\fP

.SH Member types

   Type       Definition
   value_type bool
   type       std::integral_constant<bool, value>

.SH Possible implementation

   namespace detail
   {
       template<typename T,bool = std::is_arithmetic<T>::value>
       struct is_unsigned : std::integral_constant<bool, T\fB(0)\fP < T(-1)> {};

       template<typename T>
       struct is_unsigned<T,false> : std::false_type {};
   } // namespace detail

   template<typename T>
   struct is_unsigned : detail::is_unsigned<T>::type {};

.SH Example


// Run this code

 #include <iostream>
 #include <type_traits>

 class A {};
 static_assert(std::is_unsigned_v<A> == false);

 enum B : unsigned {};
 static_assert(std::is_unsigned_v<B> == false);

 enum class C : unsigned {};
 static_assert(std::is_unsigned_v<C> == false);

 struct S { unsigned p : 1; int q : 1; };
 static_assert(
     std::is_unsigned_v<decltype(S::p)> not_eq
     std::is_unsigned_v<decltype(S::q)>
 );

 static_assert(
     std::is_unsigned_v<float> == false &&
     std::is_unsigned_v<signed int> == false &&
     std::is_unsigned_v<unsigned int> == true &&
     std::is_unsigned_v<bool> == true
 );

 int main()
 {
     std::cout << std::boolalpha << std::is_unsigned<char>::value << '\\n';
 }

.SH Possible output:

 false

.SH See also

   is_signed     checks if a type is a signed arithmetic type
   \fI(C++11)\fP       \fI(class template)\fP
   is_signed     identifies signed types
   \fB[static]\fP      \fI(public static member constant of std::numeric_limits<T>)\fP
   is_arithmetic checks if a type is an arithmetic type
   \fI(C++11)\fP       \fI(class template)\fP
   make_signed   makes the given integral type signed
   \fI(C++11)\fP       \fI(class template)\fP
   make_unsigned makes the given integral type unsigned
   \fI(C++11)\fP       \fI(class template)\fP
